Chapter 031. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections (Part 10)

Diagnosis The primary goal of diagnostic testing is to separate acute streptococcal pharyngitis from pharyngitis of other etiologies (particularly viral) so that antibiotics can be prescribed more efficiently for patients to whom they may be beneficial. The most appropriate standard for the diagnosis of streptococcal pharyngitis, however, has not been definitively established. Throat swab culture is generally regarded as such. However, this method cannot distinguish between infection and colonization, and it takes 24–48 h to yield results that vary according to technique and culture conditions. Rapid antigen-detection tests offer good specificity (90%) but lower sensitivity when implemented in routine...
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Chapter 031. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections (Part 10) Chapter 031. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections (Part 10) Diagnosis The primary goal of diagnostic testing is to separate acute streptococcalpharyngitis from pharyngitis of other etiologies (particularly viral) so thatantibiotics can be prescribed more efficiently for patients to whom they may bebeneficial. The most appropriate standard for the diagnosis of streptococcalpharyngitis, however, has not been definitively established. Throat swab culture isgenerally regarded as such. However, this method cannot distinguish betweeninfection and colonization, and it takes 24–48 h to yield results that vary accordingto technique and culture conditions. Rapid antigen-detection tests offer goodspecificity (>90%) but lower sensitivity when implemented in routine practice.The sensitivity has also been shown to vary across the clinical spectrum of disease(65–90%). Several clinical prediction systems (Table 31-3) can increase thesensitivity of rapid antigen-detection tests to >90% in controlled settings. Since thesensitivities achieved in routine clinical practice are often lower, several medicaland professional societies continue to recommend that all negative rapid antigen-detection tests in children be confirmed by a throat culture to limit transmissionand complications of illness caused by group A streptococci. The Centers forDisease Control and Prevention, the Infectious Diseases Society of America, theAmerican College of Physicians, and the American Academy of FamilyPhysicians do not recommend backup culture when adults have negative results ina high-sensitivity, rapid antigen-detection test, however, given the lowerprevalence and smaller benefit in this age group. Table 31-3 Guidelines for the Diagnosis and Treatment of AcutePharyngitis Age Diagnostic Criteria TreatmentGroup Recommendationsa Adults Clinical suspicion of Penicillin V, 500 streptococcal pharyngitis (e.g., fever, mg PO tid, or tonsillar swelling, exudate, enlarged/tender anterior cervical lymph nodes, absence of cough or coryza)b with: Amoxicillin, 500 mg PO bid, or History of rheumatic fever or Erythromycin, 250 mg PO qid, or Documented household Benzathine exposure or penicillin G, single dose of 1.2 million units IM Positive rapid strep screenChildren Clinical suspicion of Amoxicillin, 45 streptococcal pharyngitis (e.g., mg/kg qd PO in divided tonsillar swelling, exudate, doses (bid or tid), or enlarged/tender anterior cervical lymph nodes, absence of coryza) with: Penicillin VK, 50 mg/kg qd PO in divided doses (bid), or History of rheumatic fever or Cephalexin, 50 mg/kg qd PO in divided doses (qid), or Documented household Benzathine exposure or penicillin G, single dose of 25,000 units/kg IM Positive rapid strep screen or Positive throat culture (for patients with negative rapid strep screen) a Unless otherwise specified, the duration of therapy is generally 10 d, withappropriate follow-up. b Some organizations support treating adults who have these symptoms andsigns without administering a rapid streptococcal antigen test. Sources: Cooper et al, 2001; Schwartz et al, 1998. Cultures and rapid diagnostic tests for other causes of acute pharyngitis,such as influenza virus, adenovirus, HSV, EBV, CMV, and M. pneumoniae, areavailable in some locations and can be used when these infections are suspected.The diagnosis of acute EBV infection depends primarily on the detection ofantibodies to the virus with a heterophile agglutination assay (monospot slide test)or enzyme-linked immunosorbent assay. Testing for HIV RNA or antigen (p24)should be performed when acute primary HIV infection is suspected. If otherbacterial causes are suspected (particularly N. gonorrhoeae, C. diphtheriae, or Y.enterocolitica), specific cultures should be requested since these organisms maybe missed on routine throat swab culture.